Transcription

1 Monatomic Ions Ions are atoms that have either lost or gained electrons. While atoms are neutral, ions are charged particles. A loss of electrons results in a positive ion or cation (pronounced cat-eye-on ). A gain of electrons results in a negative ion or anion (pronounced an-eye-on ). Although ions and elements have similar chemical symbols, they are entirely different substances with different physical properties. A. Monatomic Ions In order to determine the charge of monatomic ions, you can use the periodic table as a guide: Group # (Column) Ion Charge Examples 1 These elements lose one electron to form +1 ions. Na +, Li +, K + 2 These elements lose two electrons to form +2 ions. Mg 2+, Ca 2+, Ba 2+ Groups 3-12 The elements in groups 3-12 are called transition metals. These elements always lose electrons to form positive ions (cations) but their charges vary. For example, iron can form a +2 or a +3 ion. In cases like these, you must be told which ion to use. Fe 2+, Fe These elements lose three electrons to form +3 ion. Al The charges on these ions vary. Carbon and silicon do not form ions. For the rest of the group, you must be given the charge. These elements gain three electrons and form 3 ions. Sn 2+, Pb 2+ N 3-, P 3-16 These elements gain two electrons to form 2 ions. O 2-, S 2-17 These elements gain one electron to form 1 ions. F -, Cl -, Br -, I - 18 These atoms do NOT form ions. Their charge is always zero. He, Ne, Ar, Kr Naming Ions (Nomenclature): Simple cations are named by saying the element and adding the word ion. Na + is called sodium ion Mg 2+ is called magnesium ion Simple anions are named by dropping the ending off the element name and adding ide. F - is called fluoride O 2- is called oxide N 3- is called nitride Note: the charge of a monatomic anion is equal to the group number minus 18.

3 Simple Binary Ionic Compounds Ionic compounds are compounds formed by the combination of a cation and a anion. (Think: metal plus nonmetal ). Ionic compounds are more commonly known as salts. Binary ionic compounds are compounds containing only two elements, as demonstrated in the examples below. When writing formulas for ionic compounds, we use subscripts to indicate how many of each atom is contained in the compound. Remember that even though ions have charges, ionic compounds must be neutral. Therefore, the charges on the cation and the anion must cancel each other out. In other words, the net charge of an ionic compound equals zero. Example 1: For a salt containing sodium ion, Na +, and chloride, Cl -, the ratio is one to one. The positive charge on the sodium ion cancels out the negative charge on the chloride. (+1) + (-1) = 0 Therefore, the formula for the salt is NaCl. (The actual formula is Na 1 Cl 1, but chemists omit subscripts of 1). Example 2: For a salt containing calcium ion, Ca 2+, and chloride, Cl -, the ratio can t be one to one. (+2) + (-1) = +1 Remember that ionic compounds must be neutral. In order to yield a neutral compound, two chlorides must bond to the calcium ion: So, the formula for this salt is CaCl 2. (+2) + 2(-1) = 0 Nomenclature: When naming ionic compounds, simply write the element name of the metal followed by the ion name of the nonmetal. (Remember: the metal ion (cation) is always written first!) NaCl is called sodium chloride, and CaCl 2 is called calcium chloride.

5 Polyatomic Ions Polyatomic ions contain two or more different atoms (polyatomic means many atoms ). Here are some common examples: a. ammonium ion, NH 4 + (the only positive polyatomic ion you need to know) b. ATE ions: contain an atom bonded to several oxygen atoms: - Nitrate = NO 3 2- Carbonate = CO 3 3- Phosphate = PO 4 - Acetate = CH 3 CO 2 2- Sulfate = SO 4 - Chlorate = ClO 3 c. ITE ions: remove one oxygen from the ATE ion and keep the same charge: - Nitrite = NO 2 - Chlorite = ClO 2 Phosphite = PO 3 3- Sulfite = SO 3 2- d. Other common complex ions: Hydroxide = OH - Cyanide = CN - Ionic Compounds Containing Polyatomic Ions As you ve already learned, ionic compounds are formed by the combination of a positive ion (cation) and a negative ion (anion). This is the same when dealing simple ions or complex ions. Be careful to note, however, that complex ions are grouped together and should not be separated. In other words, don t ever separate the sulfate ion, SO 4 2- into sulfur and oxygen. If it s written as a group, keep it as a group! Since complex ions come in groups, things can get tricky when using subscripts. As a result, we use parentheses to separate the ion from the subscript: If we need two sulfates in a compound, we write: (SO 4 ) 2. If we need three nitrates in a compound, we write: (NO 3 ) 3. And, just as before, the net charge of the compound must be zero. For a salt containing sodium ion, Na +, and nitrate, NO 3 -, the ratio would be 1:1 since the positive and negative charges cancel out. Therefore, the formula is NaNO 3 and is called sodium nitrate. (Note: no parentheses are necessary here). For a salt containing calcium ion, Ca 2+, and nitrate, NO 3 -, the ratio must be 1:2 (one calcium ion for every two nitrates). So, the formula would be Ca(NO 3 ) 2.

7 Ionic Compounds Containing Transition Metals The transition metals are the elements located in the middle of the periodic table (in groups Unlike the group 1A and 2A metal ions, the charges of transition metal ions are not easily determined by their location on the periodic table. Many of them have more than one charge (also known as an oxidation state). There are eight transition metals that you should highlight on your periodic table: Co, Cr, Cu, Fe, Mn, Hg, Sn, and Pb Each of these elements form more than one ion and therefore must be labeled accordingly. For example, iron forms two ions: Fe 2+ and Fe 3+. We call these ions iron (II) ion and iron (III) ion respectively. (See Table of Transition Metal Ions ). When naming any ion from the elements listed above, you MUST include a Roman numeral in parentheses following the name of the ion. The this roman numeral is equal to the charge on the ion. We don t include the + because all metal ions are positive. Here are two more examples: Pb 4+ = lead (IV) ion Cr 3+ = chromium (III) ion Similarly, when naming a compound containing one of these transition metals, you must include the Roman numeral as well. Iron Chloride isn t specific enough since the compound could contain either iron (II) or iron (III) ion. You must specify the charge on the iron. Iron (II) chloride contains the Fe 2+ ion. When combined with chloride, Cl -, we know the formula must be FeCl 2. Iron (III) chloride contains the Fe 3+ ion. This time, three chlorides are required to form a neutral compound. Therefore, the formula is FeCl 3. By looking at the formula of an ionic compound, we can determine the charge (oxidation state) of the metal. Example: Write the name of Co 2 O 3 1. Recognize that Co, cobalt, is a transition metal. This means that you must include a Roman numeral after its name. So, the basic name will be Cobalt ( ) Oxide. 2. To find the charge on cobalt, use oxide as a key. Oxide has a charge of 2 so three oxides will have a charge of What balances a 6 charge? A +6 charge! So, the positive half of the compound must equal Since there are two cobalt ions, the charge is split between them. So, each one has a +3 charge. Therefore, we are using the Co 3+ ion and the compound is called cobalt (III) oxide. Remember that anions (negative ions) always have a definite charge. When dealing with compounds containing transition metals, look to the anion first. Determine the charge of the anion and then solve to figure out the charge of the cation. When dealing with metals other than the transition metals, you don t need Roman numerals. In other words, calcium ion, Ca 2+ is always +2. Don t call CaCl 2 calcium (II) chloride. Its name is calcium chloride.

10 Naming Binary Covalent Compounds Binary covalent compounds come from the combination of two nonmetals (or a nonmetal and a metalloid). These compounds do not involve ions; as a result, they have a slightly different naming system. Chemists use prefixes to indicate the number of atoms in each compound. The prefixes are listed in the table below: # of Atoms Prefix 1 Mono 2 Di 3 Tri 4 Tetra 5 Penta 6 Hexa 7 Hepta 8 Octa 9 Nona 10 Deca When naming binary covalent compounds, the first element name is given followed by the second element with an ide ending. The first element gets a prefix when there is more than one atom in the compound.* The second element ALWAYS gets a prefix. Here are some examples: Compound NO* N 2 O NO 2* N 2 O 3 N 2 O 4 N 2 O 5 Name Nitrogen Monoxide Dinitrogen Monoxide Nitrogen Dioxide Dinitrogen Trioxide Dinitrogen Tetraoxide Dinitrogen Pentaoxide * Notice that the prefix mono is omitted in these cases Prefixes are necessary when naming covalent compounds because the atoms can combine in any whole number ratio. N 2 O, for example, cannot simply be called nitrogen oxide, because there are several other compounds that contain nitrogen and oxygen. We must specify that there are two nitrogen atoms bonded to a single oxygen atom. When dealing with ionic compounds, there is only one way for a cation and anion to combine to form a neutral compound. As a result, there is no need to use prefixes. This is why CaCl 2 is called calcium chloride, rather than calcium dichloride.

12 Shortcut for Formula Determination: Use the following method when asked to determine the formula of an ionic compound: 1. Write the two ions with their charges (metal first). 2. Ignoring the + or charges, crisscross the numbers and make them subscripts. 3. Then, rewrite the formula, dropping the charges. (See Examples Below) Example 1: Write the formula for calcium chloride: 1. Write the two ions with their charges (metal first). Ca 2+ Cl - 2. Ignoring the + or charges, crisscross the numbers and make them subscripts: Ca 2+ Cl - 3. Then, rewrite the formula, dropping the charges. In this case, the formula is: CaCl 2. Example 2: Write the formula for magnesium oxide: 1. Write the two ions with their charges (metal first). Mg 2+ O 2-2. Ignoring the + or charges, crisscross the numbers and make them subscripts: Mg 2+ O 2-3. Then, rewrite the formula, dropping the charges. The rewritten formula is: Mg 2 O 2. Note: Since the subscripts for the anion and cation are the same, the formula reduces to Mg 1 O 1. Therefore, the correct formula is written as: MgO.

Simple Binary Ionic Compounds Ionic compounds are compounds formed by the combination of a cation and a anion. (Think: "metal plus nonmetal"). Ionic compounds are more commonly known as "salts." Binary

Lab Session 5, Experiment 4 Chemical Nomenclature Objective: To learn how to read and write formulas of compounds Background: Many of the substances you will encounter in this laboratory are ionic compounds.

Chapter 7 Writing Formulas and Naming Compounds Chemistry Systematic Naming There are too many compounds to remember the names of all of the known compounds. Compounds are made of two or more elements.

Chemical Names & Formulas Name: Period: Date: I. WRITING IONIC FORMULAS 1. are formed by two ions of opposite charge ( are + and are -) and that they are held together by a relatively weak attraction between

Lab 5 Name How Are Ionic and Covalent Compounds Named and Represented Symbolically? PreLab Assignment There is no written prelab assignment for this laboratory exercise. Recommended: Review the element

Lab 5 Name How Are Ionic and Covalent Compounds Named and Represented Symbolically? PreLab Assignment There is no written prelab assignment for this laboratory exercise. Recommended: Review the element

Lesson 1: Interpretation of Chemical Formulas Introduction Chemical formulas are used to represent the compositions of elements and compounds (pure substances). A chemical formula expresses the qualitative

SCH3U Lesson 21 Chemical Nomenclature There are two main systems of nomenclature: IUPAC International Union of Pure and Applied Chemistry IUPAC has created a standardized set of rules used to name chemical

5. CHEMICAL BONDING All particles are held together by chemical bonds of some kind. Water molecules are made up to two hydrogen atoms and one oxygen atom always. The three atoms are held together by chemical

Nomenclature of Ionic Compounds Ionic compounds are composed of ions. An ion is an atom or molecule with an electrical charge. Monatomic ions are formed from single atoms that have gained or lost electrons.

Nomenclature Packet Worksheet I: Binary Ionic Compounds (representative metals) metals from groups 1A, 2A, and 3A (1, 2, and 13) have constant charges as ions and do NOT get Roman Numerals in their names

COMPOUNDS Compounds are pure substances that contain 2 or more elements combined in a definite proportion by mass. Compounds have unique properties compared to their component elements. For example, although

Name: Period: Activity 1 A compound by any other name Objective: Chemical Bonding POGIL Based on the elements present in a chemical formula, classify the compound as ionic or covalent (covalent molecules

I. Writing Formulas for Ionic Compounds The ions charges must (be multiplied to) make neutral compounds. We must have the same number of positive charges as negative charges, so that the total charge equals

The ate, ide, ite, per ate, hypo ite system of naming that is introduced early in general chemistry actually has a logical basis for its classification. In chemistry, structure creates function. Therefore,

Chapter 5 Naming Compounds Writing Formulas Systematic Naming There are too many compounds to remember the names of them all. Compound is made of two or more elements. Put together atoms. Name should tell

Types of Nomenclature Ionic - electrons are transferred from the metal to the nonmetal. Covalent Compound - electrons are shared between 2 nonmetals. Types of Covalent Identify the following as ionic or

In the previous section, you learned how and why atoms form chemical bonds with one another. You also know that atoms combine in certain ratios with other atoms. These ratios determine the chemical formula

UNDERSTANDING CHEMICAL FORMULAS CHAPTER 5 NAMING COMPOUNDS General information The formula tells the elements that make up a compound and the number of atoms of each element in the compound. -when a subscript

OXIDATION NUMBERS The oxidation number or state refers to the charge an atom would have if the pairs of electrons in each bond of the compound belonged to the atom with the most electronegative charge,

CHEMICAL NAMES AND FORMULAS Nomenclature Naming Monatomic Ions Monatomic ions single atom with a (+) or (-) charge Cations Group 1A, 2A, and 3A elements Name is the same as the metal followed by the word

Names and formulae of substances Think about what you call your friends. Some of your friends might have full names (long names) and a nickname (short name). These are the words we use to tell others who

Worksheet #6 Covalent (Molecular) Compounds 1. What happens when a covalent bond is formed? What keeps the species together in a covalent bond? Binary Compounds with Hydrogen 2. Write correct names for

Elements and Compounds elements combine together to make an almost limitless number of compounds the properties of the compound are totally different from the constituent elements Tro, Chemistry: A Molecular

1 POLYATOMIC IONS We have seen that atoms can lose or gain electrons to become ions. Groups of atoms can also become ions. These groups of atoms are called polyatomic ions. Examples: O hydroxide ion NO

The Language of Chemistry Chemistry has a language all of its own Ionic Compounds Chemistry Element Symbols Chemical Formulas Chemical Equations English Letters Words Sentences Each element symbol starts

NOMENCLATURE EXPERIMENT 9 OBJECTIVE The objective of this assignment is to write the names of compounds using their formulas. DISCUSSION The naming of inorganic compounds can be broken down into two areas:

Unit 6 Notepack: Chapters 9 &10 Chemical Quantities 9.1 Naming Ions NAME Period: A. ions: Ions made of single. B. Elements: There is a pattern in predicting how many electrons are lost and gained for the

Exercise # 05 INORGANIC NOMENCLATURE - NAMING INORGANIC COMPOUNDS Every compound has its own CHEMICAL FORMULA and its own NAME. The nomenclature (naming systems) for IONIC and COVALENT compounds are different.

Binary Ionic Compounds The first formulas of compounds you will write are for binary ionic compounds. A binary compound is one that is composed of two elements. Before you can write a formula, you must

Oxidation Numbers The chemical formula for water is H 2 O. Carbon Dioxide is CO 2. Why does oxygen combine in different ratios, in different compounds? Do Chemistry students need to memorize the chemical

Naming Compounds Tutorial and Worksheet Since we use different methods in naming binary covalent (molecular) compounds and ionic compounds, the first step in naming or writing the formula of a compound

Ionic Compounds and Ionic Bonding 1 Chemical Bonds There are three basic types of bonds: Ionic The electrostatic attraction between ions Covalent The sharing of electrons between atoms Metallic Each metal

Formulas and Nomenclature Formulas First of all, the formulas are the symbols for compounds and molecules. There are three different types of formulas, which are, Empirical formula Molecular formula Structural

Naming Compounds Naming compounds is an important part of chemistry. Most compounds fall in to one of three categories ionic compounds, molecular compounds, or acids. Part One: Naming Ionic Compounds Identifying

Chapter 5 - Molecules and Compounds How do we represent molecules? In pictures In formula In name Ionic compounds Molecular compounds On the course website, you will find a list of ions that I would like

Ch. 4 NAMING COMPOUNDS Nomenclature: Naming Compounds There are 2 main types of binary compound: compounds composed of 2 or more elements. 1. Ionic compound: compounds that contain a metal and a non-metal.

9 CHEMICAL NAMES AND FORMULAS SECTION 9.1 NAMING IONS (pages 253 258) This section explains the use of the periodic table to determine the charge of an ion. It also defines polyatomic ion and gives the

WRITING FORMULAE GENERAL RULES: 1. When non-metals bond to form a compound, molecules are formed. The atoms in the molecule share electrons when their orbitals with unpaired electrons overlap. These molecules

Why? Polyatomic Ions Can a group of atoms have a charge? Do you know you eat a lot of -ates? Next time you look at a food label, read the ingredients and you will likely find a number of ingredients that

Putting Ions in Their Hands Covalent, Ionic and Metallic Bonding SCIENTIFIC Introduction The first time seeing formulas and names of ionic compounds can be confusing. However, upon further investigation,

OXIDATION NUMBER Oxidation number = the charge an atom would acquire if all its bonds were treated as ionic bonds. To determine how many atoms combine with one another in a compound we must determine each

Work Session 2b: Formulas, Names, and Masses Use the information in your textbook for this work session, as well as the information on pages 4 and 5. Part 1: Binary Ionic Compounds Give the formula and

Chem 309 Name Chapter 2 Supplemental Homework Nomenclature and Formula Writing Objective The purpose of this assignment is to gain practice in using chemical nomenclature for naming compounds and writing

Classification of Ionic and Molecular Compounds and their Nomenclature Prelab Read the entire laboratory write up. Write an objective and answer the following questions in your laboratory notebook before

Compounds Chapter 2 1 Types of Matter Homogeneous matter has the same appearance, composition, and properties throughout. Heterogeneous matter has visibly different phases which can be seen, or properties

Writing Chemical Formulas Help? A chemical formula is a combination of elemental symbols and subscript numbers that is used to show the composition of a compound. Depending of the type of compound that

Chemistry What is a chemical formula? It indicates the relative number of atoms of each kind in an ionic compound. Ex Al 2 O 3 has 2 atoms of Al and 3 atoms of O. It indicates the number of atoms of each

Activity One: Binary Ionic Compounds Composed of Main Group Elements This activity focuses on the nomenclature rules for ionic compounds composed of two different elements from select groups on the periodic

Chapter 5 Page 1 Chapter 5: Molecules and Compounds Compounds-a pure substance composed of more than one type of where the combine chemically infixed, definite proportions. Contrast a compoundto a mixturewhere

Chapter 4 Compounds and Their Bonds 4.1 Octet Rule and Ions Octet Rule An octet is 8 valence electrons. is associated with the stability of the noble gases. He is stable with 2 valence electrons (duet).

Nomenclature Worksheet Part 1-Ionic compounds 1 Ionic compounds are composed of cations and anions. Most cations are made from metals. The cation is a positively charged species. Cations have fewer electrons

Name Date Class 9 CHEMICAL NAMES AND FORMULAS SECTION 9.1 NAMING IONS (pages 253 258) This section explains the use of the periodic table to determine the charge of an ion. It also defines polyatomic ion